Subaru WRX Forum banner

2007 STI won't boost higher than 5.8psi

10K views 28 replies 6 participants last post by  Ruso 
#1 ·
Hey ya'll, 2007 WRX STI all stock. Its my first STI. I got from a dealer ie Covert ford. The engine had been swapped because previous engine had being blown out. Sad to say the car was a lemon :(. I'm slowly restoring it back to its glory. My problem right now is that I can't get passed 5.8psi boost. Stock boost should be 14.5psi. I put a brand new turbocharger hose with pill from subaru. I did a boost leak test so no boost leaks, I even replace the PCV and reset the ECU. I'm starting to think the ECU was flashed with this setting at some point. Any ideas what could be causing the low boost? Thanks in advance!
 
#2 · (Edited)
if you have no boost leaks, check for exhaust leaks between the block and the turbo. ie: exhaust manifold, uppipe, and all gaskets in-between. if you have one, that could definitely cause low boost as the leak is preventing pressure from building on the hotside.

also never re-use gaskets and always use oem subaru gaskets.
 
#4 ·
Yes, as was trying to sleep last night. I was thinking I did see exhust carbon building and a little bit of oil on the power steering lines under the turbo. I was also thinking we'll may the waste gate is stuck open. I'll keep ya'll posted.
 
#6 ·
I did a smoke test with seafoam, some smoke is coming out of the waste gate arm that conects to the flapper. Will I need to replace the turbo If these items are leaking? I guess I'll need to pull out the turbo to properly inspect it. Will post pictures soon.
 
#8 ·
it sounds like the diaphragm is dead. Use a compressor an take the tube off of the wastegate an put like 10psi in it an see if it moves or if you hear air escaping out the back

If you hear air an it doesnt move.... get a new wastegate actuator.
 
#13 · (Edited)
do you mean the up-pipe going to the turbo?

the downpipe (also known as a dump pipe) dumps the exhaust out the back, and the up-pipe goes down to the header from the turbo. (if you follow the exhaust path from the cylinder, the flow goes up the uppipe and down the downpipe)

no gasket between the up-pipe and the exhaust header could easily cause your problem.
 
#17 ·
So I started to notice a low ticking sound coming from the driver side engine bay. I asume it's a exhaust leak coming from the manifold because it starts around 2.5k rpm and gets louder at 5k rpm. It starts as a inconsistent tick then at 3k rpm becomes consistent. If im not mistaken boost build up is in that range and since changing the gasket didn't make a difference in boost I'm thinking there might be some lose bolts that connect the exhaust system. Any thoughts?
 
#20 ·
After extensive research and diagrams. I've come to understand that at no point should the bypass valve allow air presure through the vacume line. I pulled the IC out and put pressure on the system and that is what it was doing. Crossing my fingers for a bad bypass valve.
 
#23 ·
Im sorry I usually want people to fix things themselves an take on there ownership of their vehicle. But you aren't following what people are asking you.

Find a shop that deals with subies and have them fix it. You are just buying random shizzz an hoping it fixes it.
 
#26 ·
:nerd:

See you don't know what you are talking about and instead of following what we had original said to do you have done your own thing. You and your extensive research has gotten you nothing and listening to people trying to help you while you giving better detailed info would have helped you find the issue by now.

The line that goes to the BPV actually DOES sees vacuum and boost. The Boost along with the spring inside it helps keep it closed during boost. when your foot comes off the pedal boost quickly becomes vacuum and it opens up the bpv and send the air back into the intake before the turbo keep all of the measured air with-in the system.

Either follow this list of things to do in order, bring it to a professional since your not one, or sell your car before you break it so no one gets it... your call.

1 - Compression test
2 - Install NEW NGK spark plugs. I have seen first hand and with others that they fail even after 500 miles and will cause no/low boost
3 - Leak down test
4 - Check Boost control solenoid
5 - Check wastegate actuator, Apply a hand pump a see if reacts as you push air into it.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top